New Drywall = Varying TexturesThe root of the problem is that new, finished drywall will present you with three different textures, each with differing absorption rates:
- Sanded Joint Compound ("Mud"): These are the sanded-down joints and screw holes.
- Unsanded Drywall Paper: This is the bare drywall paper that lies outside of mudded areas. It has not been touched with the sander.
- Sanded Drywall Paper: This is drywall paper beyond mudded areas that has been scuffed from the sander. Expert drywall installers can minimize scuffing, but few DIYers are experts. Thus, some of this paper will become porous and fuzzy.
What Drywall Primer DoesDrywall primer does two things. First, it equalizes base colors of mud and paper, so that the paint colors can truly shine without interference.
With new finished drywall, you will have two base colors: the color of the paper (gray, off-white, or green) and the color of the mud (white or off-white). One coat of flat latex will go a long way towards covering up these colors; thicker drywall primer or "hiding paint" will completely cover them up.
Second, drywall primer soaks into paper, scuffed paper, and mud--areas of differing porosity--and creates a uniformly porous surface for the finish paint coat to stick.
Have you ever look at a painted wall from a sharp angle and seen the finished joints show through? This is an effect called "joint banding" or "photographing." Drywall primer will reduce or completely eliminate that effect.
Best Drywall Primer to Use: How About Three "Bests"?
- Flat Latex Paint: If you're not a professional drywall installer seeking utter perfection, then flat latex is your ticket to inexpensive drywall priming. In fact, many drywall manufacturers (such as USG) recommend plain flat latex paint as a drywall primer.
- Benjamin Moore Super Hide: Super Hide takes the concept one more step. Super Hide is still flat latex, but it is slightly thicker and has more color-hiding properties than plain flat latex. There are a lot of "hiding paints" on the market, and any one is just as good as Super Hide. Just make sure that it is compatible with drywall, though.
- Sheetrock Brand First Coat: Finally, First Coat, by USG, takes drywall priming to its logical conclusion. First Coat is pricier than flat latex or "hiding paints," but it's specially formulated for drywall priming. It contains a vinyl acrylic binder and calcium carbonate filler to equalize surface textures.
How to Apply Drywall PrimerManufacturers of drywall primer recommend a roller, sprayer, or brush. I concur with the first two, but not the last one. Except for touching up small, stubborn areas, brushes smear the drywall primer too much.
For the roller, use a high quality cover with 1/8" to 1/4" nap.